1-4y = x , 1-4y = 2-2y, 1-2y = 2, -2y = 1 , y = -0.5
2-y = x+y, 2= x+2y, x = 2-2y , 2+0.5 = x -0.5, 2.5 = x -0.5, x=3
y=-0.5
x = 3
Проверка. 1-4(-0.5) = 3, 1+2 = 3, 2+0.5 = 3-0.5, 2.5 = 2.5
С = пD
D = C : п
D = 81,64 : 3,14
D = 26 см
R = 1/2D
R = 26 *1/2
R = 13 см
1)8-а=8-8=0 при а =8
2)8-а=8-0=8 при а =0
3)0<8
Решение:x - 2 =
20 - x² = x² + 4x + 4
16 - 2x² + 4x = 0
x² - 2x - 8 = 0
D₁ = k² - ac = 1 + 8 = 9;
= 3
x₁ = 1 + 3 = 4
y₁ = x - 2 = 2
x₂ = -2
y₂ = -4
Ответ: (4; 2), (-2; -4)